[Pw_forum] using ev.x

[Stefano Baroni]

How about trying to fit a very accurate set of data around the minimum  
with a parabola and calculate thus the bulk modulus? Have you tries to  
plot the resulting fitted curves? which one fits best the raw data?  
Udaygiri: in Science (as well as in Life) there is no free lunch ...  
Enjoy Science, no less than Life. SB

On Sep 8, 2009, at 9:04 PM, udayagiri sai babu wrote:

>
> hi all
> i am using ev.x file given in the pw_tools directory to calculate  
> bulk modulus and lattice parameter values of chromium. i used  
> murnaghan equation of state to fit my data i got bulk modulus of 256  
> gpa where as my experimental  value is 160 gpa but when i used keane  
> equation of state to fit the same data i got 148 gpa bulk modulus
>
> why is this much variation? which equation of state should i use for  
> cr? because for vanadium and Ti murnagan euation of state has given  
> reasonable (<20% error) values of bulk modulus but not for Cr
>
> please give some suggestions
> -- 
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
>
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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